In recent years, the CDMA2000 1xEV-DO (Code division Multiple Access 2000 1x Evolution Data Only) standard has been developed as a next-generation high-speed radio communication protocol. As a standard obtained by standardizing an HDR (High Data Rate) standard which is a CDMA2000 1x expansion standard, this CDMA2000 1xEV-DO standard has been standardized as Std. T-64 1S-2000C.S.0024 “CDMA2000 High Rate Packet Data Air Interface Specification” in the Association of Radio Industries and Businesses (ARIB), and is a standard obtained by expanding ARIB T-53 (in Japan) and EIA/TIA/IS-95 (in the US and Korea and the like) that is designed in order to improve communication speeds by further specializing for data communication a CDMA2000 1x standard that has been compatible with the third-generation standard (3 G) (see, for example, Patent document 1 described below).
Currently, communication networks that employ a CDMA2000 1x EV-DO standard (referred to below as an EV-DO standard) is concentrated in limited areas such as urban areas. Because of this, in a communication area that is not compatible with the EV-DO standard, radio communication terminals for the EV-DO standard perform communication by first performing a hand-down to the CDMA2000 1x standard (referred to below as a 1x standard) that is common nationwide, while in a communication area that is compatible with the EV-DO standard, communication is performed by establishing an EV-DO standard communication connection (i.e., establishing a communication session layer) by establishing a session with a base station and performing session configuration using SMP (Session Management Protocol) which is a communication protocol for the EV-DO standard. Here, ‘establishing a session’ refers to a state in which an identification ID known as a UATI (Unicast Access Terminal Identify) is allocated from the network side to a radio communication terminal. “Session configuration” is the carrying out of negotiations such as exchanging parameters relating to the setting of protocols when communication is being performed using the EV-DO standard.
Note that radio communication terminals for the EV-DO standard are described below as AT terminals (i.e., Access Terminals).    [Patent document 1] Japanese Patent Application Laid-Open (JP-A) No. 2005-136615